1. Priority Claim
This application claims the benefit of priority from Korean Patent Application No. 5149/2006, filed Jun. 8, 2006, which is incorporated by reference.
2. Technical Field
The present invention relates to a liquid crystal display device (LCD), and more particularly, to an LCD capable of reducing a discharging phenomenon.
3. Related Art
A cathode ray tube (CRT) can be heavy and large-sized. Therefore, a flat panel display device to overcome drawbacks of the CRT is under active development. The flat panel display device includes liquid crystal display devices (LCDs), field emission displays (FEDs), plasma display panels (PDPs), electro-luminescence (EL) display devices, etc.
FIG. 1 is a schematic view of a related art LCD. In FIG. 1, a power supply unit 11 generates and/or supplies various voltages. The power supply unit 11 may generate and/or supply a power voltage VCC, a reference voltage VDD, and a gate voltage Vg. The power voltage VCC drives a timing controller 1, a gate driver 3, and a data driver 5. The reference voltage VDD is used by the common voltage generating unit 13 to generate a common voltage Vcom. The gate voltage Vg is supplied to a liquid crystal panel 7 via the gate driver 3.
The timing controller 1 receives the power voltage signal VCC and generates a control signal for controlling the gate driver 3 and the data driver 5. In response to a control signal, the gate driver 3 supplies the gate voltage Vg to the liquid crystal panel 7. Additionally, in response to the control signal, the data driver 5 supplies a predetermined data voltage to the liquid crystal panel 7. In response to the reference voltage VDD supplied from the power supply unit 11, the common voltage generating unit 13 generates the common voltage Vcom. The common voltage Vcom is supplied to the liquid crystal panel 7. Based on an electric potential difference between the data voltage and the common voltage, the liquid crystal panel 7 displays an image.
The operation of the LCD may be controlled by a power switch 9. The power switch 9 may couple an external power source to the power supply unit 11. When the power switch 9 is turned on, external power VCC is supplied to the power supply unit 11 and an image can be displayed on the liquid crystal panel 7. On the contrary, when the power switch 9 is turned off, the external power VCC is not supplied to the power supply unit 11. When the external power VCC is not supplied to the power supply unit 11, the power supply unit 11 cannot generate and/or supply the various voltages to the timing controller 1, the data driver 5, the gate driver 3, and the common voltage generating unit 13. Upon removal of the external power VCC, the liquid crystal panel 7 will discharge over a period of about several seconds, and the liquid crystal panel 7 will eventually stop displaying an image.
In FIG. 2, when the power switch 9 is turned off, the common voltage Vcom supplied to the liquid crystal panel 7 is gradually discharged to a ground voltage due to a resistance and a capacitance of the liquid crystal panel 7. This discharge occurs over a period of about several seconds. Therefore, although the power switch 9 is turned off, a residual voltage remains on the liquid crystal panel 7, and thus a discharging phenomenon can occur. The discharging phenomenon can create an abnormal image that is displayed on the liquid crystal panel 7 which reduces image quality and degrades the product quality of the liquid crystal device.
Therefore, there is a need for an LCD that is capable of reducing a discharge phenomenon and improving image quality.